Pressure cylinder for hydraulic brakes



Dec. 14, 1948. ROY 2,456,325-

PRESSURE CYLINDER FOR HYDRAULIC BRAKES Filed July 31, 1944 19'. 5INVENTOR.

LBERT 5. Roy;

fiatented Dec. 14, 194

OFFICE 2,456,325 PRESSURE CYLINDER FOR HYDRAULIC BRAK Albert E.Roy,Glendale, Calif.

Application July 31, 1944, Serial No. 547,426 11 Claims. (01. 60 54.6)

This invention relates to a pressure cylinder i for hydraulic brakes,such as are used on motor vehicles, and is a re-file of my formerapplication,

'Serial No. 446,147, filed June 6, 1942, and now abandoned.

An object of my invention is to provide a novel pressure cylinder forhydraulic brakes, whereby the initial movement of an operating levercauses sufficient pressure to be transmitted to the pressure cylindersof the braking system to actuate a .brake shoe into initial contact withthe braking surface of a brake drum, while further movement of theoperating lever causes a high pressure to be applied to the brakecylinders for braking purposes.

Another object of my invention is to provide a novel pressure cylinderfor hydraulic brakes in which the foot pressure against the operatinglever will gradually increase as the brakes are set, thus providing abrake system in which the feel is the same as with hydraulic brakes nowin general use.

Still another object of my invention is to provide a novel high-pressurecylinder for hydraulic A feature of my invention resides in the novelmeans of opening a valve and permiting liquid under pressure from thepipe lines to flow back into the primary cylinder when the pistons inthe pressure cylinders are retracted.

Other objects, advantages and features of invention may appear from theaccompanying drawing, the subjoined detailed description and theappended claims.

In the drawing:

Fig. 1 is a vertical sectional view of my pressure cylinder forhydraulic brakes and showing the pistons in retracted position, and

Fig. 2 is a side elevation of a modified form of pressure cylinder forhydraulic brakes with parts broken away to show interior construction.

Referring more particularly to the drawing, my pressure cylinder forhydraulic brakes comprises a primary cylinder I and a high-pressurecylinder 2, The high-pressure cylinder is smaller in diameter than theprimary cylinder, and is arranged co-axially therewith. A liquidreservoir 3 is arranged above the primary cylinder I, and an inlet port4 permits liquid to flow back and forth between the reservoir and theprimary cylinder.

A primary piston 5 is slidably mounted in cylinder 1 and is providedwith an annular packing ring 6 to prevent leakage past the piston. Thepiston 5 is of hollow cup-shaped formation and one-half itsnormal size,further force exerted defines a chamber I4 tubular hub or shank 9.

located within the piston and open at its outer end. A high-pressurepiston l is slidably mounted in the high-pressure cylinder 2, and isprovided with suitable annular packing 8 to prevent leakage. A tubularhub or shank 9 connects the pistons 5 and l and serves as a conduitthrough which liquid may flow from the chamber l4 to the high pressurecylinder.

A low-pressure piston H3- operates within the chamber I4 of the primarypiston 5 and moves longitudinally of the, piston 5 under the urge ofoperating mechanism, such as the brake pedal. The push rod ll engagesthe low-pressure piston l0 and this push rod is actuated by the brakepedal in a usual and well-known manner. A hollow sleeve l2 extendsforwardly from the lowpressure piston IE) and closely fits within the Aport I3 is formed through the'wall of the sleeve and communicates withthe inside of the chamber E4 of the primary piston 5, permitting liquidto pass from the lowpressure chamber M of piston 5 into the brakingformed inthe inner end of the primary piston 5 to prevent fluid frombeing pushed back into the 'reservoir 3 when the low-pressure piston 5is moved forwardly and the brakes are applied. A

coil spring .l in chamber l4 has one end bearing pressure piston Ill andurges this piston into its I released or retracted position, as shown inFig. 1.

The high p-ressure piston l is formed with a central bore I8 extendingentirely therethrough, and this bore is controlled by a ball valve 49.The ball valve is normally urged against its seat by the spring 20. Apipe 2| extends from the outer end retracted position. A trip finger 23is pivotly mounted on the piston l and is adapted to engage and unseatthe ball valve l9. action occurs when the drag rod 24 is pulled Thisunseating rearwardly on retraction of the low-pressure pistonlO. Thedragrod 24 is pivotly attached at one -end'to the finger 23 and is slidablymounted through the spider 25 of the low-pressure piston Ill, Thestrength of spring is somewhat less than that of spring 22, thuspermitting piston ID to move inwardly within chamber l4 upon theinitialapplication of force through push rod ll. However the strength ofspring I! is sufficient through rod H and piston 10 causes inwardmovement of hollow piston 5 and high pressure piston 1 against theaction of spring 22. Move- .ment of high pressure piston I of courseimmedi- "cylinder, a

3 ately increases the pressure in cylinder 2 over that in chamber I4 andcauses valve I9 to close.

The operation of my pressure cylinder, thus far described, is asfollows: 011 the initial pressure of the brake pedal, the rod II willcause the lowpressure piston to move forwardly in chamber 14 of thepiston 5. The valve 15 is then immediately closed. The liquid under somepressure in the chamber [4 passes through the port l-3, thence throughthe hollow hub or shank 9, past the ball check 1 9, and thence throughthe pipe M to the brake cylinders for initially filling the pipelinesand also setting the brake shoes against the brake drums. As previouslydescribed further pressure against the rod Ill will cause the primarypiston to be pushed forwardly and with it the high-pressure piston I.The necessary high pressure to actuate the brake mechanism is thusprovided, and under these high-pressures the valve 19 will close. Whenthe brake pedal is released, the low pressure piston H] is draggedrearwardiy, thus tripping the valve [9, through medium of the rod 24.Liquid can then fiowback to completely fill the chamber l4, ready forthe necessary stroke of the pressure cylinder. If the chamber 14 is notentirely filled, the static pressure of liquid in the reservoir Swillopen the valve l5, thus completely filling the chamber H1. The port 4 isopen at all times, and consequently liquid from the reservoir will fillthe primary cylinder ahead of the piston 5.

In Fig. 2, I have shown a slightly modified form of pressure cylinderfor hydraulic brakes, including a primary cylinder 26, a high-pressurecylinder 21, and a primary piston 28, which is connected to thehigh-pressure piston by the hollow hub or shank 29. A low-pressurepiston 30 is reciprocally mounted in the chamber of the hollow piston28, the same as previously described. In this modification, however, thereservoir 3! is ftapped directly into the chamber of piston 28, throughthe flexible pipe 32 connected with the inlet of the chamber by a checkvalve 32-a which opens toward the chamber. An elongated slot 33 throughwhichfthe valve 32-0. passes permits the pipe 32 to move back and forth,as the piston 28 reciprocates. The balance of the structure is the sameas previously described. The operation of the modified form of pressurecylinder is the same as previously described.

I claim:

l. A pressure "cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder supplied therefrom, a high-pressurecylinder arranged co-axially with the primary cylinder and being ofsmaller diameter "than the primary cylinder, a piston element extendingthrough said primary cylinder and into said high-pressure cylinder andhaving a cup-shaped piston head ato'ne end operating in the primarycylinder amidefining a low pressure chambenand'a piston head at itsother end operating in the high-pressure low-pressure pistonreciprocally mounted in the chamber oi the piston head opcrating in theprimary cylinder, means for actuating said low-pressure piston, saidpiston element having a passageway extending longitudinally therethroughfrom the chamber of the lowpressure piston to the high-pressurecylinder,

valve means controlling said passageway to permit fluid to pass from thelow-pressure chamber to the high-pressure cylinder, during initialoperation of the piston element on its compression stroke and preventinreturn flow of liquid from said high-pressure cylinder to saidlow-pressure 4 chamber during completion of its compression stroke, andvalve-tripping means operatively connected to said low-pressure pistonand adapted and arranged to tripsaid valve means on retraction of saidlow-pressure piston.

2. A pressure cylinder for hydraulic brakes comprising a primarycylinder, means for supplying liquid to said primary cylinder, ahigh-pressure cylinder co-axial with the primary cylinder, a pistonelement common to both cylinders, a hollow piston head on one end of thepiston element disposed within the primary cylinder and defining achamber, a piston head on the other end of the piston element, disposedwithin the high-pressure cylinder, a low-pressure piston reciprocallymounted within the chamber of the first-named piston head, spring meansin said hollow piston urging it inwardly and said low-pressure pistonoutwardly, means to actuate said low-pressure piston, said pistonelement having liquid passage extending longitudinally therethrough,from the chamber of the low-pressure piston to the highpressurecylinder, valve means controlling said fluid passage, and meansoperative upon retraction of said low pressure piston to open said valvemeans and permit fluid to return to said chamber.

3. A pressure cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder, an open port connecting the reservoir andthe primary cylinder, a high-pressure cylinder coaxial with the primarycylinder, a piston element common to both cylinders, a hollow pistonhead on one end of the piston element operating Within the primarycylinder and defining a chamber, a piston head on the other end of thepiston element, operating within the high-pressure cylinder, alow-pressure piston reciprocally mounted within the chamber of thefirst-named piston head, spring means in said chamber bearing againstthe low-pressure piston and urging the same outwardly and bearingagainst the forward Wall of said hollow piston and urging the sameinwardly, means to actuate said low-pressure pis- 'ton and force thesame inwardly, said piston element having a liquid passage extendinglongitudinally therethrough from the chamber of the low-pressure pistonto the high-pressure cylinder, valve means controlling said liquidpassage, a second valvein the first-named piston head, closing on thecompression movement of the lowpressure piston and opening on retractionof said low-pressure piston, and means for opening said "first valveupon retraction of said low pressure piston.

4. A pressure cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder, an o'p'en'port connecting the reservoirand the primary cylinder, a high-pressure cylinder coaxial with theprimary cylinder, a piston element common to both cylinders, a hollowpiston head on one end of the piston element disposed within the primarycylinder and defining a chamber, a piston head on the other end of thePiston element, disposed within the high-pressure cylinder, alow-pressure piston reciprocally mounted within the chamber of thefirst-named piston head, spring means in said chamber bearing "againstthe low-pressure piston and urging the same outwardly, means to actuatesaid low-pressure piston, said piston element having liquid passageextending longitudinally therethrough, from the chamber of thelow-pressure piston to the high-pressure cylinder, valve meanscontrolling saidjliquid passage, and tripping means 'operativelyconnected to the low-pressure piston and engaging said valve means,whereby said valve means is released on retraction of the lowpressurepiston.

5. A pressure cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder, an open port connecting the reservoir,and the primary cylinder, a high-pressure cylinder ooaxial with theprimary cylinder, a piston element common to both cylinders, a hollowpiston head on one end of the piston element disposed within the primarycylinder and defining a chamber, a piston head on the other end of thepiston element disposed within the high-pressure cylinder, alow-pressure piston reciprocally mounted within the chamber of thefirst-named piston head, spring means urging against the low-pressurepiston toward a retracted position, means to actuate said low-pressurepiston, said piston element having liquid passage extendinglongitudinally therethrough, from the low-pressure piston to thehigh-pressure cylinder, valve means controlling said liquid passage,tripping means operatively connected to the low-pressure piston andengaging said valve means, whereby said valve means is released onretraction of the low-pressure piston, and a second valve in thefirstnamed piston head, closing on the compression movement of thelow-pressure piston and opening on retraction of said low-pressurepiston.

6. A pressure cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder supplied therefrom, a high pressurecylinder coaxial with said primary cylinder, a piston element common toboth cylinders, a hollow piston head on one end of said piston elementdisposed Within said primary cylinder and defining a chamber, a pistonhead on the other end of said piston element disposed within saidhigh-pressure cylinder, a low-pressure piston reciprocally mountedwithin said chamber, means for actuating said low-pressure piston, saidpiston element having a liquid passage extending longitudinallytherethrough from said chamber to said high-pressure cylinder, valvemeans controlling said passage, and tripping means operatively connectedto said low-pressure piston and adapted to trip said valve means onretraction of said low-pressure piston.

7. A pressure cylinder for hydraulic brakes comprising a liquidreservoir, a primary cylinder supplied therefrom, a high pressurecylinder coaxial with said primary cylinder, a piston element common toboth cylinders, a hollow piston head on one end of said piston elementdisposed Within said primary cylinder and defining a chamber, a pistonhead on the other end of said piston element disposed within saidhigh-pressure cylinder, a low-pressure piston reciprocally mountedWithin said chamber, means for actuating said low-pressure piston, saidpiston element having a liquid passage extending longitudinallytherethrough from said chamber to said high-pressure cylinder, valvemeans controlling said passage, and means operative upon retraction ofsaid low pressure piston to open said valve and permit fluid to returnto said chamber.

8. A pressure cylinder for hydraulic brakes comprising a primarycylinder, a high pressure cylinder coaxial with said primary cylinder, apiston element common to both cylinders, a hollow piston head on one endof said piston element disposed within said primary cylinder anddefining a chamber, a piston head on the other end of said pistonelement disposed within said high-pressure cylinder, a low-pressurepiston reciprocally mounted within said chamber, means for actuatingsaid low-pressure piston, said piston element having a liquid passageextending longitudinally therethrough from said chamber to saidhigh-pressure cylinder, valve means controlling said passage, and meansoperative upon retraction of said low-pressure piston to open said valveand permit fluid to return to said chamber.

9. A pressure cylinder. for hydraulic brakes comprising a primarycylinder of relatively large diameter, a high-pressure cylinder of lessdiameter coaxial with said primary cylinder, a piston element common toboth cylinders having a piston head on the end thereof in saidhigh-pressure cylinder, a low-pressure piston reciprocally mounted insaid primary cylinder having an inner portion slidable within saidcommon piston element, means for actuating said low-pressure piston,said piston element having a liquid pass- Number 10. A pressure cylinderfor hydraulic brakes comprising a primary cylinder of relatively largediameter, a high-pressure cylinder of less diameter coaxial with saidprimary cylinder, a piston element common to both cylinders having apiston head on the end thereof in said highpressure cylinder, alow-pressure piston reciprocally mounted in said primary cylinder, meansfor actuating said low-pressure piston, said piston element having aliquid passage extending longitudinally therethrough from said primarycylinder to said high-pressure cylinder, valve means controlling saidpassage, and means operative upon retraction of said low-pressure pistonto open said valve and permit fluid to return to said primary cylinder.

11. A pressure cylinder for hydraulic brakes comprising a primarycylinder of relatively large diameter, a high-pressure cylinder of lessdiameter coaxial with said primary cylinder, a piston element common toboth cylinders having a piston head on the end thereof in saidhighpressure cylinder, a low-pressure piston reciprocally mounted insaid primary cylinder, means for actuating said low-pressure piston,said piston element having a liquid passage extending longitudinallytherethrough from said primary cylinder to said high-pressure cylinder,valve means controlling said passage, and valve tripping means operativeby retraction of said low pressure piston to open said valve and permitfluid to return to said primary cylinder.

ALBERT E. ROY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Leuschner Nov. 26, 1935 FOREIGN PATENTSCountry Date France Nov. 11, 1935 Number

